Guest-dependent mechanical anisotropy in pillared-layered soft porous crystals – a nanoindentation study

Abstract

Soft porous crystals (SPCs) of the type [Zn₂(L)₂(dabco)]_n (L = linear dicarboxylate linker, dabco = 1,4-diazabicyclo[2.2.2]octane) show exceptional mechanical anisotropy. Single-crystal nanoindentation experiments reveal very large changes of the elastic modulus and hardness triggered by exchange of the guests adsorbed in the porous metal–organic framework. The substantial variations of the mechanical properties as a function of the guest molecules can be explained by the responsive nature of these SPCs. Based on non-specific guest–framework interactions, crucial changes of the network geometry induce a complex and dynamical mechanical behaviour.